Porous composite product particularly with high specific surface area, method for preparing and electrode for electrochemical assembly formed with a porous composite film

ABSTRACT

The invention concerns a porous composite product in particular with high specific surface area, characterised in that it is formed of a polymeric material and at least 20% of one or several fillers, and in that the product is obtainable by extrusion. The invention also concerns a method for preparing a porous composite product characterised in that it consists in: a) forming a mixture containing one or several insoluble polymers, one or several soluble or calcinable polymers, one or several fillers; b) extruding said mixture for forming an extruded precursor product; c) eliminating the soluble or calcinable polymer(s) of the extruded precursor product; recuperating the porous composite product. The invention also concerns all extruded object consisting of a porous composite product in particular with high specific area. Finally it concerns an electrode formed of a film of porous composite product.

[0001] The invention relates to a porous composite product, inparticular in the form of a film, in particular with a high specificsurface, and to a process for the preparation of such a product.

[0002] It also relates to the precursor composite product of use incarrying out the said process.

[0003] It also relates to the application of the porous compositeproduct in the form of a film as electrode for the entire range ofelectrochemical products and to the application in general of the porouscomposite product, with a high specific surface, in the field ofselective membranes, of packaging or of catalysis.

[0004] Low density porous films are already known, in Particular byPatent Application EP-A-283,187, which are obtained by spinning, at themelting temperature, a mixture of a first thermoplastic polymer and of asecond thermoplastic polymer and then removing the second polymer bymeans of an appropriate solvent. Such a porous film can be used forvarious applications, in particular in the field of filtration or ofseparation.

[0005] Patent Application EP-A-430,439 discloses a process for improvingthe production of such films, in which a mixture of a firstthermoplastic polymer and of a second immiscible thermoplastic polymeris extruded through a die and then removing the immiscible polymer bymeans of a solvent, the process being characterized in that a perforatedbarrier plate is interposed upstream of the die, so as to obtain aporous structure comprising a longitudinal region of low porosity andanother longitudinal region of higher porosity.

[0006] Furthermore, polarizable electrodes are known which can be usedin electrical capacitors of the double-layer type which are capable ofbeing charged with, or of discharging, a large amount of electriccharge.

[0007] The polarizable electrodes which can be used in supercapacitorsare based on an ideally polarizable material which is light and whichhas a large exchange surface area, such as active charcoal, which is acarbonaceous material with a high specific surface, in particulargreater than 1000 m²/g.

[0008] For an electrode to exhibit the maximum efficiency, it must havea maximum proportion of active mass and an optimum accessibility to thismass. The latter property requires that it should have an open porousstructure. This is the case, for example, with electrodes made ofactivated fabric: an active charcoal fabric is manufactured from afabric based on viscose or on polyacrylonitrile, which fabric iscarbonized and then activated.

[0009] However, such electrodes are expensive and exhibit a high anduneven thickness (generally greater than 300 μm). Furthermore, althoughsuch a production method makes it possible, at least in theory, toemploy a spooling technology, it turns out in practice that such anoperation is difficult to carry out.

[0010] Electrodes with a very high proportion of active mass (generallygreater than 98%) can also be obtained by sintering. Active charcoal andvarious additives, in particular conducting black, are mixedmechanically with a liquid until a suspension is obtained. The solutionobtained is poured over a filtering partition, which is placed underpartial vacuum. After a certain time, all the components are depositedhomogeneously on the filtering partition, whereas the liquid has passedthrough this partition. The partial vacuum creates a degree of cohesionbetween the components, equivalent to compacting under pressure. Theelectrode is the dry material recovered on the partition.

[0011] However, as above, this technology exhibits numerousdisadvantages. In particular, it lends itself with difficulty to the useof a spooling technology and the thickness, homogeneity and evenness ofthe electrodes are difficult to control. Furthermore, the processes arelimited in the choice of the polymers. In particular, polyolefins cannotbe used.

[0012] The carbonaceous filler can also be mixed mechanically with abinding polymer in a small proportion, for example 3% of Teflon, until avery viscous paste is obtained, and then rolling in order to give asheet which is cut up using a hollow punch in order to produce anelectrode.

[0013] This process results in the same disadvantages as the precedingproduction methods.

[0014] A process for manufacture by coating is also mentioned, in whichprocess the active filler and one or more additives, such as a bindingpolymer, are mixed with a solvent until a paste of controlled viscosityis obtained. The latter is coated onto a support sheet which can actsubsequently as current collector. The sheet passes into an oven inorder for the solvent to be evaporated.

[0015] The deposit can be relatively thin (down to a few microns) andhomogeneous and the proportion of active mass is high.

[0016] It is nevertheless a process which is difficult to implementbecause of the possible use of solvents which can be toxic.

[0017] The electrodes in the form of films, in particular of polyolefinfilms, which make it possible to employ a spooling technology are alsoknown.

[0018] These polarizable electrodes are based on a carbonaceousmaterial, for example an active charcoal with a high specific surface,in particular at 1000 m²/g, and on a binder, such as polyolefins, inparticular polyethylene or polypropylene, or other polymers, such aspolyesters, polycarbonates or polyimides.

[0019] Polarizable electrodes using a polyethylene or polypropylenebinder and an active charcoal powder have been provided, for example(JP-A-22062/92).

[0020] However, polarizable electrodes based on a binder such aspolyethylene or polypropylene exhibit a very low porosity.

[0021] Such phenomena also occur with the other binders cited above.

[0022] Document BE-A-693,135 discloses porous sheets ofpolytetrafluoroethylene entirely in the form of fibrils comprisingconducting filler materials, such as graphite or a metal, up to 98% ofthe weight of the sheet.

[0023] This type of structure is obtained by mixing an aqueousdispersion of polytetrafluoroethylene particles with an extractablepolymer, followed by milling. This milling constitutes a critical stagewhich results in the shearing of the polytetrafluoroethylene particlesand the conversion of the particles into a network of elongated fibers.Extrusion is then carried out and then the extractable polymer isremoved. The final structure exhibits pores of greater than 0.1 μm.These sheets can be used as electrode in fuel cells.

[0024] The abstract of Japanese document JP-A-57100142 discloses theproduction of a porous membrane which consists in extruding a mixture,by volume, of 15-60% of a polyolefin resin; 3-40% of a polyether; 20 to80%, by volume, of an extractable, finely divided powder; and 0.5 to 10%of an insoluble powder and in then extracting the polyether and theextractable powder. The Applicant has confirmed that it is impossible bythe process disclosed in this document to obtain sheets comprising ahigher proportion of filler without seriously affecting the mechanicalproperties.

[0025] It would therefore be desirable to produce porous electrodesformed of a binder and of fillers, in particular with a high specificsurface, which can be produced in a large amount which make it possibleto employ a spooling technology.

[0026] The aim of the present invention is specifically to provide asolution to this technical problem.

[0027] One object of the present invention is to provide novel porouscomposite products having in particular a high specific surface.

[0028] Another object of the present invention is to provide compositefilms, in particular with a high specific surface, with a high contentof fillers, which make it possible to employ a spooling technology.

[0029] Another object of the present invention is to make it possible touse a broad choice of polymers.

[0030] Another object of the present invention is to provide porouscomposite products or films which are inexpensive to manufacture.

[0031] Another object of the present invention is to make it possible toobtain products of varied shape, because of the extrusion techniqueused, which can be employed, such as pipes, rods, films or any otherextruded object.

[0032] Another object of the present invention is to providecarbonaceous electrodes in the form of thin, homogeneous, ideallypolarizable porous films which exhibit a very high proportion of activemass.

[0033] Another subject-matter of the present invention relates to theapplications of the porous composite products as selective membrane,packaging films or insulating films.

[0034] The invention firstly relates to a porous composite product, inparticular with a high specific surface, characterized in that itcomprises a polymeric material and at least 20% of one or more fillers,in particular with a high specific surface, the said product beingcapable of being obtained by extrusion.

[0035] The expression “product” is intended to denote an assembly, thecohesion of which is sufficient for it to retain its integrity withoutbeing supported.

[0036] It is significant to note that the products according to theinvention exhibit a novel structure because of the very high homogeneityof the distribution of the filler, in particular with a high specificsurface, in the polymeric material and because of its continuousstructure. Furthermore, the polymeric material is non-fibrillated.

[0037] This is one of the essential characteristics of the productaccording to the invention, as the Applicant has observed that a productwhich does not exhibit a sufficient homogeneity results in inadequatemechanical properties for the level of fillers indicated above.

[0038] The expression “capable of being obtained by extrusion” meansthat the composite product exhibits the characteristics of an extrudedproduct.

[0039] In order for the product “capable of being obtained by extrusion”to exhibit the required homogeneity, it is necessary for this extrusionto be carried out on a mixture which is as homogeneous as possible. Sucha homogeneous mixture can be obtained from a twin-screw extruder. Otherappropriate mixers can also be used.

[0040] The products concerned are therefore fundamentally different fromthose which can be obtained by the coating technique as was described inthe preamble of the description.

[0041] Preferably, one of the essential characteristics of the porouscomposite product according to the invention is that it exhibits a highspecific surface.

[0042] The specific surface is evaluated by the “BET” measurement asdescribed, for example, in the publication Technique de l'ingénieur [Artof the Engineer], Pbis 45-1 (Etude de structure—mesure de surfacespécifique) [Structure study—measurement of specific surface), JeanCharpin and Bernard Rasneur.

[0043] The specific surface of the porous composite product according tothe invention is greater than approximately 10 m²/g and preferablygreater than 20 m²/g. Advantageously, of between 20 m²/g and 100 m²/g.

[0044] The porosity of the product is, by volume, greater than 5%. It isgenerally less than approximately 80%.

[0045] For applications in supercapacitors or accumulators, the porosityis generally between 15 and 50%.

[0046] This mean diameter of the pores is generally less than 1 μm.According to a preferred alternative form, the mean diameter of thepores is less than 0.5 μm, preferably less than 0.1 μm, advantageouslyless than 0.02 μm.

[0047] In the specific case of fluorinated polyolefins, the diameter ofthe pores is generally less than 0.5 μm. This is the case in particularwith polytetrafluoroethylene.

[0048] In addition to the high BET specific surface and the mechanicalproperties, these products are noteworthy in that the electrochemicalcapacity is greater than 2 F/g, preferably greater than 10 F/g.

[0049] In the case of an electrode for a supercapacitor, capacitor, thedesired porosity is mesoporous, whereas, in the case of Belgian Patent693,135, which relates to an electrode for “fuel cell” application, thedesired porosity must be open (macroporous) in order to allow a highfuel flow.

[0050] In the case of porous composite products in the form of films, itshould be noted that these films exhibit noteworthy mechanicalproperties which allow them to be employed by the spooling technology.In general, these films exhibit a tensile strength at break of greaterthan 4 MPa, advantageous of greater than 6 MPa, at room temperature.

[0051] Mention may be made, among fillers, of carbons, such as graphitesor carbon blacks with a low specific surface, metal oxides, silica ortalcs.

[0052] Mention is in particular made, among fillers with a high specificsurface which are suitable for the production of such compositeproducts, of carbonaceous materials or inorganic and metallic particleswith a high specific surface, such as, for example, Raney metals, rareearth metal oxides, porous ceramics, or perlites, zeolites or clays.

[0053] The properties required for a carbonaceous material are anexpanded surface per unit of high weight, a low electrical resistanceand good electrochemical chemical stability.

[0054] The carbonaceous materials can be provided in the form of powdersand are obtained, for example, from oil pitch, phenolic resins, coconutshells and other organic products.

[0055] An active charcoal exhibits in particular a specific surface(BET) of between 300 and 3000 m²/g, preferably of greater than 1000m²/g.

[0056] The polymeric material is formed of thermoplastic plasticelastomers or polymers which are insoluble in aqueous and/or organicsolvents and which ensure the cohesion of the product (structuralpolymers or elastomers) and of thermoplastic polymers or elastomers withpolar groups which remain in the product after the implementation of themanufacturing process which results in the said porous product or film.

[0057] Mention is in particular made, among insoluble elastomers orpolymers, of polyolefins, such as polypropylenes, polyethylenes orcopolymers of ethylene and of propylene. These polyolefins are such thatthey can be produced in the form of films and are well known inparticular as packaging films. They are, for example, low or highdensity polyethylene optionally comprising, as copolymer, a greater orlesser proportion of an alpha-olefin.

[0058] They may also be polyamides, such as polyether-block-polyamides,polyimides, vinyl copolymers with a high proportion of ethylenemonomers, such as poly(ethylene/vinyl acetate) with a high proportion ofethylene monomers, acrylic polymers, aromatic polymers, such aspolystyrenes, for example polystyrene-butadiene copolymer, fluorinatedpolymers, such as poly(vinylidene fluoride), or copolymers formed frommonomers belonging to one of the abovementioned families, for examplevinylidene fluoride and hexafluoropropylene copolymers or vinylidenefluoride and trifluoroethylene copolymers.

[0059] The thermoplastic elastomers or polymers which are insoluble inthe solvents are preferably chosen from the group of the polyolefins.

[0060] Mention is in particular made, among the soluble polymers, ofpolymers which are soluble in the following solvents: water, alcohols,dimethylformamide, dimethyl sulfoxide, tetrahydrofuran or acetone.

[0061] With the proviso, of course, that the degree of polymerization isappropriate to removal by solvent, the soluble polymers are inparticular chosen from polyethers, such as polyoxyethylene orpolyoxopropylene, propylene, or polyalcohols, such as poly(vinylalcohol) or ethylene-vinyl alcohol copolymers. Mention is in particularmade, among these polymers, of those for which the molecular mass isbetween 200,000 and 1,000,000, advantageously polyethers.

[0062] Mention is also made of polymers which can be calcined accordingto the usual methods.

[0063] The calcinable polymers correspond to the polymers which aresoluble in the solvents mentioned above and can also be chosen frompolymers with a decomposition temperature below that of the structuralpolymer or elastomer, for example cellulose.

[0064] The choice of these polymers can be made in a known way by simpletests within the scope of a person skilled in the art.

[0065] The composite product preferably comprises at least 20% by weightof fillers, advantageously between 30 and 90%, preferably between 50 and85%.

[0066] The composite product preferably comprises 10 to 40% ofthermoplastic polymers or elastomers which are insoluble in aqueousand/or organic solvents and 5 to 40% of polymers which are soluble inaqueous and/or organic solvents.

[0067] More preferably, the composite product comprises:

[0068] 10 to 40% of polyolefin,

[0069] 5 to 40% of polyether,

[0070] fillers, q.s. for 100%.

[0071] Another characteristic of the porous composite product accordingto the invention lies in the fact that it is provided in a homogeneousand even form, that is to say that the fillers are intimately mixed withthe polymeric material, unlike, for example, the sheets obtained bycoating a mixture of carbonaceous fillers with a small proportion ofbinding polymer of the polytetrafluoroethylene type.

[0072] The composite products according to the invention can be providedin the form of a film and exhibit the advantage of being able to beemployed using spooling technology.

[0073] These films avoid the use of a support.

[0074] The invention also relates to a process for the preparation of acomposite product as described above, characterized in that:

[0075] a) a mixture comprising one or more insoluble polymers, one ormore soluble or calcinable polymers and one or more fillers with a highspecific surface is formed,

[0076] b) the said mixture is extruded, so as to form an extrudedprecursor product,

[0077] c) the soluble or calcinable polymer or polymers is/are removedfrom the extruded precursor product,

[0078] d) the porous composite product is recovered.

[0079] The said process is therefore an extrusion-removal process whichmakes it possible to obtain a porous composite product-with a highspecific surface.

[0080] The expression “removed” is intended to indicate that asubstantial portion of the soluble or calcinable polymers is eliminatedin order to form pores, it being understood that it is not very probablethat these polymers will be completely removed, due in particular totheir affinity for the active charcoal.

[0081] In phase a) of the process, all the constituents, namely one ormore solvent-insoluble polymers which correspond to the polymericmaterial forming the structure of the composite product, one or moreother solvent-soluble or calcinable polymer or polymers and one or morefillers with a high specific surface, are homogeneously mixed, whetherby dissolving or suspending, it being known that the polymers ensuringthe cohesion of the composite product (insoluble polymers) and thefillers with a high specific surface are not removed during stage c).The mixing can also be carried out by means of the extruder which allowsstage b) to be carried out.

[0082] From among the soluble polymers which will be removed duringstage c) may be chosen any soluble polymer which can be mixed accordingto stage a) and mention is in particular made of polymers which aresoluble, for example, in water, alcohols, dimethylformamide, dimethylsulfoxide, tetrahydrofuran or acetone.

[0083] With the proviso, of course, that the degree of polymerization isappropriate to removal by solvent, the soluble polymers are chosen inparticular from polyethers, such as polyoxyethylene or polyoxypropylene,or polyalcohols, such as poly(vinyl alcohol) or ethylene/vinyl alcoholcopolymers.

[0084] Mention is also made, by way of polymers which can be removed inorder to form pores, of polymers which can be calcined according to theusual methods.

[0085] The calcinable polymers can be chosen from polymers with adecomposition temperature below that of the structural polymer orelastomer, for example cellulose.

[0086] The choice of these polymers can be made in a known way by simpletests within the scope of a person skilled in the art.

[0087] The various constituents of the product are mixed at anappropriate temperature, in particular by means of an extruder. In thiscase, stages a) and b) are carried out simultaneously in order to givean intermediate precursor product exhibiting a very low BET specificsurface (less than approximately 1 m²/g).

[0088] The precursor product can be re-extruded in the form of a film,in particular a thin film with a thickness of less than approximately300 μm.

[0089] According to an advantageous alternative form, stage b) istherefore carried out in two stages:

[0090] a first extrusion stage (i) consisting in forming granules,

[0091] a second extrusion stage (ii) consisting in forming a film.

[0092] The first stage is advantageously carried out in a corotatingtwin-screw extruder, with a rod die for example, whereas the secondstage is advantageously carried out in a single-screw extruder with aflat die.

[0093] The extruded precursor product, either in the form of granules orin the form of films, is subsequently subjected to the removal stage c)in which the soluble polymer is eliminated.

[0094] This removal stage can be carried out in particular by dissolvingthe soluble polymer by bringing it into contact with an appropriatesolvent.

[0095] A calcination can also be carried out according to a knownprocess which consists in slowly raising the temperature up to thedecomposition temperature of the polymer to be removed.

[0096] The products are subsequently recovered and exhibit a “BET”specific surface of greater than approximately 10 m²/g, preferably ofgreater than approximately 20 m²/g.

[0097] Another subject-matter of the invention is therefore the porouscomposite products with a high specific surface formed of a polymericmaterial and of one or more fillers with a high specific surface,characterized in that they are capable of being obtained by theextrusion-removal process as described above.

[0098] Another subject-matter of the present invention is the precursorproducts obtained before the removal stage, these precursor products, ofuse in particular in carrying out the process described above, compriseone or more solvent-insoluble polymers, one or more othersolvent-soluble or calcinable polymers and one or more fillers with ahigh specific surface.

[0099] The insoluble polymers/soluble or calcinable polymers ratio byweight is preferably between 0.1 and 5, advantageous 0.1 and 2.

[0100] The proportion of fillers with a high specific surface in thesolvent-free mixture leading to the precursor product is preferablybetween 20 and 60% by weight.

[0101] The invention also relates to an electrode in the form of a film,which electrode is formed of a porous composite product with a highspecific surface according to the invention.

[0102] These electrodes in the form of porous films can generally beused for the production of electrochemical chemical assemblies, such asaccumulators, double-layer capacitors or supercapacitors.

[0103] The supercapacitors are formed in a known way of two polarizableelectrodes and of a separator impregnated with an electrolyte. Theseassemblies are also denoted by the term “electrolytic double-layercapacitor”.

[0104] The electrodes according to the invention greatly improve thecapacity of the films, in particular by the very high proportion ofactive mass which can be obtained.

[0105] Particular mention is made of the following fields ofapplications:

[0106] Porous electrodes for the electrochemical storage of energy[electrochemical generators, redox accumulators, air accumulators,electrochemical supercapacitors or double-layer capacitors, or fuelcells].

[0107] Porous electrodes for electrodialysis processes [production ofdrinking water, production of salt from sea water, demineralization oforganic products (wheys, milk, wine, and the like), desalination ofwater for consumption, softening of boiler water or decontamination ofnuclear power station effluents].

[0108] Porous electrodes for capacitive deionization processes[production of drinking water, production of salt from sea water,demineralization of organic products (wheys, milk, wine, and the like),desalination of water for consumption, softening of boiler water ordecontamination of nuclear power station effluents].

[0109] Porous electrodes for electrolysis processes [production ofchlorine and sodium hydroxide, electrolysis of water or production ofacid and a base from a salt].

[0110] Electromembranes for dialysis and electrodialysis processes[production of drinking water, production of salt from sea water,demineralization of organic products (wheys, milk, wine, and the like),desalination of water for consumption, softening of boiler water ordecontamination of nuclear power station effluents].

[0111] Electromembranes for filtration processes [selectiveelectrofiltration of organic products or microfiltration].

[0112] The invention also relates to the application of these compositeproducts in the form of granules or films:

[0113] to methods for filtration and for adsorption, for exampledehumidification of gaseous or liquid surroundings, selective adsorption(physical and/or chemical), molecular sieves or filtration of pollutedair,

[0114] to catalysis,

[0115] to energy exchanges (for example, thermal or sound insulation orheat exchangers),

[0116] to packaging, in particular the packaging of delicate productsrequiring selective permeability.

[0117] The invention is now illustrated by the following examples, givenby way of indication:

EXAMPLE 1

[0118] The proportions by mass of the starting compounds (powders) areas follows:

[0119] 40% active charcoal (with a specific surface of 1250 m²/g)

[0120] 20% ethylene-propylene copolymer

[0121] 40% polyoxyethylene (POE 300,000).

[0122] The combined powdered constituents are mixed as homogeneously aspossible by mixing by means of a corotating twin-screw extruder with alength of 40D and with two kneading regions and three transportationregions. The device used is a twin-screw with a diameter of 58 mm andthe temperature profile used is as follows:

[0123] 50/120/120/110/110/100/100/120/120/150/170.

[0124] Die pressure: 8 MPa

[0125] Number of revolutions per minute: 85

[0126] Throughput: 34 kg/h.

[0127] The granules obtained are introduced into a single-screw with alength of 30D for extrusion of a primary mixture. The device used is atwin-screw with a diameter of 30 mm and the temperature profile used isas follows:

[0128] 165/170/170/170/185° C.

[0129] Die pressure: 8 MPa

[0130] Number of revolutions per minute: 10

[0131] Throughput: 2 kg/h.

[0132] The film obtained has a thickness of 200 μm.

[0133] The following stage consists in immersing the film obtained inwater at room temperature for a residence time of 5 minutes. The film isthen dried at 40° C. for 1 hour.

[0134] The mean proportions by mass of the compounds after treatment areas follows:

[0135] 52% active charcoal

[0136] 26% ethylene-propylene copolymer

[0137] 22% polyoxyethylene.

[0138] It is possible to metallize with aluminum (for example: 0.5 Ω/□the films obtained, before or after treatment, in a metallizing deviceat a pressure of the order of 0.01 Pa (10-4 mbar).

[0139] The physical characterization of the films obtained, metallizedor otherwise, results in the following data:

[0140] elongation at break (see table below)

[0141] spooling tension (core with a diameter of 6 mm): 0.05 g/μm/mm

[0142] electrochemical capacity of 26 F/g of electrode (measured via theslope of the discharge curve of the supercapacitor, in galvanostaticmode)

[0143] “BET” specific surface of less than 1 m²/g of film at the outletof the extrusion and “BET” specific surface of 28 m²/g of film afterpassing into water according to the method which consists in immersingthe electrode for approximately five minutes.

EXAMPLE 2

[0144] The proportions by mass of the starting compounds (powders) areas follows:

[0145] 40% active charcoal (with a specific surface of 1250 m²/g)

[0146] 10% ethylene-propylene copolymer

[0147] 50% polyoxyethylene (POE 300,000).

[0148] The combined powdered constituents are mixed as homogeneously aspossible by mixing by means of a corotating twin-screw extruder with alength of 25D and with two kneading regions and three transportationregions. The device used is a twin-screw with a diameter of 19 mm andthe temperature profile used is as follows: 160/170/180/190/200° C.

[0149] Die pressure: 10.5 MPa

[0150] Number of revolutions per minute: 400

[0151] Throughput: 1.8 kg/h.

[0152] The granules obtained are introduced into a single-screw with alength of 30D for extrusion of a primary mixture. The device used is atwin-screw with a diameter of 30 mm and the temperature profile used isas follows: 160/170/180/190/220° C.

[0153] Die pressure: 17.5 MPa

[0154] Number of revolutions per minute: 15

[0155] Throughput: 2.5 kg/h. The film obtained has a thickness of 180μm.

[0156] The next stage consists in immersing the film obtained in waterat room temperature for a residence time of 5 minutes. The film is thendried at 40° C. for 1 hour.

[0157] The mean proportions by mass of the compounds after treatment areas follows:

[0158] 60% active charcoal

[0159] 15% ethylene-propylene copolymer

[0160] 25% polyoxyethylene.

[0161] It is then possible to metallize with aluminum (for example: 0.5Ω/□ the films obtained in a metallizing device at a pressure of theorder of 0.01 Pa (10−⁴ mbar).

[0162] The physical characterization of the films obtained, metallizedor otherwise, results in the following data:

[0163] elongation at break (see table below)

[0164] spooling tension (core with a diameter of 6 mm): 0.05 g/μm/mm

[0165] electrochemical capacity of 26 F/g of electrode according to themethod described in Example 1

[0166] “BET” specific surface of less than 1 m²/g of film at the outletof the extrusion and “BET” specific surface of 60 m²/g of film afterpassing into water according to the method described in Example 1.Mechanical characterization measurement of the films obtained ElongationModulus of at break elasticity Force Temperature Film (%) (Dn/mm²) (Mpa)20° C. Example 1 0.97 134 8.3 20° C. Example 2 0.89 170 9.3 40° C.Example 1 1.14 88 6.1 40° C. Example 2 1.20 125 7.2 60° C. Example 15.73 22 2.0 60° C. Example 2 1.68 30 2.6

EXAMPLE 3

[0167] The proportions by mass of the starting compounds (powders) areas follows:

[0168] 40% active charcoal (active charcoal with a specific surface of1250 m²/g)

[0169] 20% ethylene-propylene copolymer

[0170] 40% polyoxyethylene (POE 300,000).

[0171] The combined powdered constituents are mixed as homogeneously aspossible by mixing by means of a corotating twin-screw extruder with alength of 40D and with two kneading regions and three transportationregions. The device used is a twin-screw with a diameter of 58 mm andthe temperature profile used is as follows:

[0172] 50/120/120/110/110/100/100/120/120/150/170.

[0173] Die pressure: 8 MPa

[0174] Number of revolutions per minute: 85

[0175] Throughput: 34 kg/h.

[0176] The next stage consists in immersing the granules obtained (2mm/² mm) in water at room temperature for a residence time of 5 minutes.The film is then dried at 40° C. for 1 hour.

[0177] The mean proportions by mass of the compounds after treatment areas follows:

[0178] 60% active charcoal

[0179] 15% ethylene-propylene copolymer

[0180] 25% polyoxyethylene.

[0181] The granules obtained exhibit an expanded surface of 30 m²/g.

1. Porous composite product, characterized in that it is formed of apolymeric material and at least 20% of one or more fillers and in thatthe said product is capable of being obtained by extrusion.
 2. Porouscomposite product according to claim 1, characterized in that itexhibits a high specific surface.
 3. Composite product according toclaim 1 or 2, characterized in that the mean diameter of the pores isless than 0.5 μm.
 4. Composite product according to claim 1,characterized in that the polymeric material comprises elastomers orpolymers chosen from the group consisting of polyolefins, which areoptionally fluorinated, acrylic polymers, aromatic polymers, polyamides,polyimides, vinyl polymers with a high proportion of ethyl monomers andoptionally thermoplastic polymers or elastomers, soluble in polarorganic solvents or water, which remain after the implementation of themanufacturing process.
 5. Composite product according to claim 4,characterized in that the polymeric material comprises elastomers orpolymers chosen from the group consisting of polyethylenes,polypropylenes, ethylene-α-olefin copolymers and optionallythermoplastic polymers or elastomers, soluble in polar organic solventsor water, which remain after the implementation of the manufacturingprocess.
 6. Composite product according to either of claims 4 and 5,characterized in that the thermoplastic elastomers, soluble in polarorganic solvents or water, which remain after the implementation of themanufacturing process are chosen from polyethers, poly(vinyl alcohol)sor ethylene-vinyl alcohol copolymers, preferably polyethers with amolecular mass of between 200,000 and 1,000,000.
 7. Composite productaccording to claim 6, characterized in that the composite productcomprises: 10 to 40% of polyolefin, 5 to 40% of polyether, fillers, q.s.for 100%.
 8. Composite product according to claim 1, characterized inthat the filler is chosen from fillers with a high specific surface,composed in particular of active charcoal, inorganic particles ormetallic particles.
 9. Composite product according to claim 8,characterized in that the filler exhibits a specific surface of between300 and 3000 m²/g.
 10. Composite product according to one of thepreceding claims, characterized in that it comprises between 30% and 90%by weight of filler.
 11. Composite product according to claim 10,characterized in that it comprises 50 to 85% by weight of filler. 12.Composite product according to one of the preceding claims,characterized in that it exhibits a “BET” specific surface of greaterthan 10 m2/g, preferably of greater than 20 m²/g.
 13. Composite productaccording to one of the preceding claims, characterized in that it isprovided in the form of a film.
 14. Composite product according to claim13, characterized in that the product in the form of a film exhibits atensile strength at break of greater than 4 Mpa, preferably of greaterthan 6 MPa.
 15. Composite product according to one of claims 1 to 12,characterized in that it is provided in the form of granules. 16.Process for the preparation of a porous composite product according toone of claims 1 to 15, characterized in that: a) a homogeneous mixturecomprising one or more insoluble polymers, one or more soluble orcalcinable polymers and one or more fillers, in particular with a highspecific surface, is formed, b) the said mixture is extruded, so as toform an extruded precursor product, c) the soluble or calcinable polymeror polymers is/are removed from the extruded precursor product, in orderto form pores, d) the porous composite product is recovered. 17.Preparation process according to claim 16, characterized in that theremoval of stage c) is carried out by bringing the extruded precursorproduct into contact with an appropriate solvent.
 18. Preparationprocess according to claim 17, characterized in that the removal ofstage c) is carried out by subjecting the extruded precursor product toa calcination.
 19. Preparation process according to claim 16,characterized in that stage a) is carried out by means of a mixer or ofa twin-screw extruder, ensuring homogeneous mixing of the polymers andof the fillers, in particular with a high specific surface. 20.Preparation process according to one of claims 16 to 19, characterizedin that the insoluble polymer/soluble or calcinable polymer ratio byweight is between 0.1 and
 5. 21. Extruded composite precursor product ofuse in particular in carrying out the process according to one of claims16 to 19, comprising one or more insoluble polymers, one or more othersoluble or calcinable polymers and one or more fillers, in particularwith a high specific surface.
 22. Electrode for an electrochemicalassembly, such as an electrochemical generator or accumulator,characterized in that it is formed of a film of porous composite productaccording to claim 13 or 14 with an electrochemical capacity of greaterthan 2 F/g, preferably of greater than 10 F/g, and of anelectrochemically chemically active material.
 23. Electrode for asupercapacitor or capacitor, characterized in that it is formed of afilm of porous composite product according to claim 13 or 14,characterized in that the electrochemical capacity is greater than 2F/g, preferably greater than 10 F/g.
 24. Electrochemical assembly, inparticular an electrochemical generator, capacitor or supercapacitorcomprising two electrodes according to claim 22 or 23 and a separatorimpregnated with an electrolyte.
 25. Application of the compositeproducts according to either of claims 13 and 14 for the electrochemicalstorage of energy.
 26. Application of the composite products accordingto either of claims 13 and 14 for packaging or insulation. 27.Application of the composite products according to one of claims 1 to 12and 15 for selective filtration.
 28. Application of the compositeproducts according to either of claims 13 and 14 for electrodialysis orcapacitive deionization processes.
 29. Application of the compositeproducts according to either of claims 13 and 14 for the electrolysisprocess.